Major ion chemistry and atmospheric CO2 consumption deduced from the Batal glacier, Lahaul-Spiti valley, Western Himalaya, India

This study mainly focuses on the source identification of various ions in meltwater and estimation of CO2 consumption rate by chemical weathering in the Batal glacier basin on the basis of 2 years of study (2015 and 2017). The glacier meltwater has been monitored as slightly acidic in nature having mean pH value of 6.6. Ca2+ was observed as the most dominant cation contributing about 76% of TZ(+) (total cations), whereas SO42- was observed as the most dominant anion contributing about 70% of TZ(-) (total anions) in the stream meltwater. High ratios of (Ca + Mg) versus TZ(+) (mean value: 0.89 +/- 0.02) and (Ca + Mg) versus (Na + K) (mean value: 8.51 +/- 2.07) elucidate that stream water chemistry of the Batal glacier is largely controlled by carbonate weathering. Concentration of total dissolved solid in the glacial stream water was higher during the low-melt season (September) and lower during the high-melt period (July). The average value of daily mean TDS flux of the study area was calculated to be 12.4 t/day. The mean values of CWR (carbonate weathering rate) and SWR (silicate weathering rate) for the Batal glacier basin were calculated to be 97.4 and 22.8 t/km(2)/year, showing higher contribution of CWR as compared to SWR in the investigation area. CO2 consumption rate by the combined silicate and carbonate (chemical) weathering was estimated to be 11.1 x 10(5), 28.8 x 10(5) and 35.5 x 10(5) mol/km(2)/year during the study period September 2015, June 2017 and July 2017, respectively. The annual CO2 drawdown by the Batal glacier basin on the basis of CO2 consumption rate by chemical weathering is much lower as compared to the Gangotri glacier, which may be due to bigger size and higher meltwater runoff of the Gangotri glacier as compared to the Batal glacier.